The present invention relates to semiconductor devices and method for fabricating the same, specifically a semiconductor device having a damascene interconnect structure and a method for fabricating the same.
In recent years, an interconnect structure including copper (Cu) and a low dielectric constant insulating film in order to increase speed and integration density has been developed in a semiconductor integrated circuit using silicon (Si). In the case of the interconnect structure including Cu, interdiffusion between a Cu layer (interconnect body layer) and a peripheral insulating film is likely to occur during various thermal treatments performed in processes to form an integrated circuit, and the Cu layer easily reacts with oxygen (O) in an oxygen atmosphere to form a Cu oxide film. Thus, before forming the Cu layer, it is necessary to form a barrier film made of tantalum (Ta), tantalum nitride (TaN), and the like. In particular, when the Cu layer is buried in an interlayer insulating film as in the case of the damascene interconnect structure, the diffusion of Cu atoms into the interlayer insulating film becomes significant, and thus it is essential to form the diffusion barrier film.
In order to ensure the reliability of the interconnect structure including Cu, existing processing technologies require a barrier film having a thickness of 10 nm or larger. Moreover, in order to reduce interconnect resistance along with a future reduction in interconnect width, it is required to reduce the thickness of the barrier film by generations. However, in a conventional method for forming a barrier film, it is difficult to uniformly and homogeneously form the barrier film in an interconnect groove and a sidewall of a via hole (interconnect connecting hole). Therefore, problems with the reliability of the interconnect structure arise, where an example of the problems is that barrier properties of the barrier film, interface adherence between the barrier film and the Cu layer, and resistance against electromigration due to interfacial diffusion cannot be ensured.
As a method capable of solving these problems and reducing the thickness of the barrier film, it has been proposed that metal added to the Cu layer is diffused through a thermal treatment into the interface between the Cu layer and the insulating film to allow the reaction of the diffused metal with the insulating film, thereby forming an stable compound, which is used as the barrier film.
A method in which a barrier film is formed in a self-aligned manner by using an element such as manganese (Mn) which rapidly diffuses in Cu and reacts with oxygen in an insulating film has been described, for example, in Japanese Patent Publication No. 2005-277390.